Vent apparatus

ABSTRACT

A vent apparatus for use in a mold defining an opening that includes a vent tube portion configured to extend through the opening of the mold and a secondary tube portion configured to mate with the first end portion of the vent tube portion. For example, the secondary tube portion may be used to seal the passageway at the first end portion and may define one or more membrane regions configured to melt during a mold process to unseal the passageway.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/791,072 filed on Mar. 15, 2013, which isincorporated by reference herein in its entirety.

BACKGROUND

The present disclosure relates to vent apparatus for use in venting theinside of a rotational mold to outside of the mold.

Rotational molding involves heating a flowable material in a hollow moldand rotating the mold to melt and distribute the material over theinside of the mold. Rotational molding is a high temperature, lowpressure process and the strength required from the molds is minimal,which results in its ability to produce large, complex parts using alow-cost mold. Further, the low processing pressure involved inrotational molding has the added advantage of producing parts that arevirtually stress free.

Rotational molded articles are used for many different commercial orconsumer purposes including but not limited to livestock feeders,drainage systems, food service containers, instrument housings, fueltanks, vending machines, highway barriers, road markers, boats, kayaks,childcare seats, light globes, tool carts, planter pots, playing balls,playground equipment, headrests, truck/cart liners, and air ducts.

The process of rotational molding generally includes placing a flowablematerial such as, e.g., a polymer usually in a powder form, inside amold. Often, the mold is composed of two or more parts and totallyencloses the powder. Molds may be made out of steel, aluminum, and/oranother metal and may be supported by a steel frame. The mold is thenplaced in an oven and heated for a predetermined amount of time to allowthe flowable material to turn into a liquid state. The mold is rotatedin two perpendicular axes throughout the rotational molding process. Asthe mold heats up, the flowable material begins to coalesce to theinside walls of the mold. The heat distribution around the inner surfaceof the mold may be determined by the outside design of the mold. Forexample, tin may be used to reduce heat in areas and gas lines may beused to radiate, or deliver, more heat on, or to, other areas similar toa convection oven.

Centrifugal forces additionally contribute to the accumulation of theflowable material around the inside of the mold (e.g., such centrifugalforces may constantly pull the material against the inside surface ofthe mold as the mold is rotated about the two respective axes). After aselected period of time, the mold may be cooled. Rotation of the moldmay continue throughout the cooling process. Once the flowable material(e.g., polymer) has hardened (after the cooling process has completed),rotation can stop, the mold may be opened, and the mold part can beremoved from the mold.

Along with the flowable material, gases (e.g., air, oxygen, nitrogen,carbon dioxide, etc.) are located inside the mold during the moldingprocess. The gases may exercise significant rates of thermal expansionin comparison to the flowable materials inside the mold. Since the moldmay be sealed tight, the pressure inside the mold may fluctuate (e.g.,increase and/or decrease) due to the temperature fluctuations of thegases located inside the mold during the heating and cooling steps ofthe rotational molding process. The pressure fluctuations may cause“blowholes” and/or deformations in the article being molded.

To counter these pressure fluctuations, a “vent tube” may be placed inthe mold to allow the inside of the mold to “breathe” to the outside ofthe mold. In other words, the vent tube may allow the pressure inside ofthe mold to equalize with the pressure outside of the mold. Typically, awad of furnace filter or steel wool is placed in the vent tube toprevent any flowable material (e.g., polymer) from falling out of themold through the vent tube as the mold rotates. Tape may also be used tocover the end of the vent tube located inside of the mold. The wad offurnace filter or steel wool and/or the tape may be burned off after aselected time period during a heating cycling of the rotational moldingprocess such that, e.g., the vent tube can breathe. Often, suchpractices may result in clogged vent tubes, which may cause a resistancein airflow (e.g., which may cause improper molding or blowholes).

Many molds may not fully seal at the points where the mold comestogether (which may be called parting lines). Often, the mold may ventthrough the parting lines prior to the flowable material solidifying, orhardening, and thereby blocking the parting lines. If airflow in a venttube is restricted after the parting lines have become blocked, the airpressure inside the mold will rise as the temperature inside the moldrises. Likewise, as the mold begins to cool, the pressure inside themold will begin to fall as the temperature inside falls. During thecooling process, the gas inside the mold may be sealed from the outsideof the mold as the polymer completely coats the entire inside of themold. If the vent remains restricted, a vacuum may be created within themolded part that may cause “blowholes” along the parting lines as gastries to enter the mold to relieve the vacuum. Additionally, as thepolymer hardens during the cooling process, the vacuum may suck aportion, or part of the molded article away from the mold wall and causea deformed or “scrap” part.

Vents may be used as one-way valves, which may be reliant on thepressure differential of the gas inside the mold to the gas outside themold, which may provide a positive pressure inside the mold at the endof the heating cycle such that a vacuum may not be created during thecooling phase. Such one-way valve system may have an inability tocontrol pressure that builds up in the mold. A silicone tube used as avent tube is disclosed in U.S. Pat. App. Pub. No. 2005/0167887 publishedAug. 4, 2004 to Rory Jones, which is incorporated herein by reference inits entirety.

SUMMARY

The present disclosure may include vent apparatus that may be used witha rotational mold. The vent apparatus may include a vent tube portion(e.g., a cylindrical pipe formed of TEFLON, etc.) and a secondary tubeportion (e.g., formed of silicone) configured to mate with the vent tubeportion. The secondary portion may mate with the vent tube portionmultiple different ways and have multiple different shapes and sizes. Inat least one embodiment, the secondary portion may define a flat, orplanar, surface that extends perpendicular to an axis along which thevent tube portion extends. The flat surface may define one or more, or aplurality, of slits therethrough to allow airflow therethrough in eitherdirection (e.g., from inside the mold to outside of the mold and fromoutside of the mold to inside of the mold). In at least one embodiment,the secondary tube portion does not exceed the diameter of the vent tubesuch that when mated, they define the same diameter (e.g., to slide intoa vent hole of a mold).

One exemplary vent apparatus may include a silicone tube that can beinserted into a polytetrafluoroethylene (PTFE), or TEFLON, tube that isalready in a valve port. Such an embodiment can be a more efficient wayof acting as the valve to relieve negative or positive pressure insideof the mold. One or more embodiments described herein may be capable ofserving as a two-way valve depending on the function needed during themolding processes (e.g., cooling, heating, etc.).

One exemplary vent apparatus includes a silicone tube defining a valveconfigured to be inserted in a PTFE tube. The PTFE may be located insidea mold. The valve of the silicone tube may equally support both ingressand egress airflow inside and outside of the mold. In a rotation mold,the valve may support egress airflow when needed as well as ingressairflow when the atmospheric pressure favors ingress or egress airflowrespectively.

One exemplary vent apparatus may provide enhanced durability andmaximized airflow for longer periods of time. Although the main tube isshown as a PTFE tube, any existing vent tube including PTFE and metalvent tubes may be modified to include the silicone rubber tubetherewith. The secondary tube portion may be a molded item that can bedefined as a component piece, as a plug, which therefore can act as avalve which will allow ingress or egress airflow dependent on the stateof air pressure inside and/or outside the rotational mold.

One exemplary vent apparatus may include a vent tube portion extendingfrom a first end region to a second end region along an axis anddefining an opening extending from the first end region to the secondend region and a secondary tube portion configured to mate with thefirst end region of the vent tube portion (e.g., the secondary tubeportion may define a surface extending perpendicular to the axis whenthe secondary tube portion is mated with the first end region, thesurface may define a plurality of slits therethrough to allow airflowthrough the surface from the opening of the vent tube to outside of thesurface, etc.).

One or more embodiments of the vent apparatus may include one or more ofthe following features: a surface of the secondary tube portion mayextend perpendicular to the axis and may allow airflow from outside ofthe surface to flow into the opening of the vent tube portion and mayallow airflow from inside the opening of the vent tube portion tooutside of the surface substantially equally; the secondary tube portionmay be configured to be mated around the outside of the vent tubeportion; the secondary tube portion may be configured to be mated in theinside of the vent tube portion; and/or the vent tube portion may definea stepped region configured to mate with the secondary tube portion

Another exemplary vent apparatus for use in a mold defining an openingmay include a vent tube portion configured to extend through the openingof the mold (e.g., the vent tube portion may extend from a first endregion to a second end region along an axis and may define a passagewayextending from the first end region to the second end region, whereinthe vent tube portion may define an inner surface and an outer surface,etc.) and a secondary tube portion configured to mate with the first endregion of the vent tube portion to seal the passageway at the first endregion (e.g., the secondary tube portion may include an inner surfaceand an outer surface along an axis, the inner surface may extend over atleast a portion of the outer surface of the vent tube portion, the outersurface may extend within and along at least a portion of the innersurface of the vent tube portion, etc.). The secondary tube portion mayfurther define one or more membrane regions configured to melt during amold process to unseal the passageway.

One or more embodiments of the vent apparatus may include one or more ofthe following features: the vent tube portion may define a vent tubeouter diameter (e.g., the first end region of the vent tube portion maydefine a mating region having a mating region outer diameter that isless than the vent tube outer diameter); the first end region of thevent tube portion may define a mating region and the mating region maydefine a mating region length extending along the axis (e.g., thesecondary tube portion may define a secondary tube portion length thatis longer than the mating region length); the vent tube portion maydefine a vent tube outer diameter (e.g., the secondary tube portion maydefine a secondary tube portion inner diameter that is less than thevent tube outer diameter); the first end region of the vent tube portionmay define an annular protrusion extending radially from the outersurface of the vent tube portion configured to engage the secondary tubeportion when the secondary tube portion is mated to the first endregion; the one or more membrane regions of the secondary tube portionmay include a plurality of membrane regions; the one or more membraneregions of the secondary tube portion may include a membrane regionextending perpendicular to the axis when the secondary tube portion ismated to the first end region; the one or more membrane regions of thesecondary tube portion may include at least one membrane regionextending parallel to the axis when the secondary tube portion is matedto the first end region; the secondary tube portion may include acylindrical body extending from a proximal end region to a distal endregion and defining a channel from the proximal end region to the distalend region (e.g., the secondary tube portion may further include an endsurface portion covering the channel at the distal end region, whereinthe end surface portion may define a membrane region of the one or moremembrane regions, etc.); the end surface portion may include only amembrane region at the center thereof; the cylindrical body may defineat least one membrane region of the one or more membrane regions; and/orthe passageway of the vent tube portion may define an innercross-section area taken perpendicular to the axis and each of the oneor more membrane regions of the secondary tube portion define an area(e.g., a combined area of all of the areas of the one or more membraneregions may be greater than the inner cross-section area of thechannel).

One exemplary vent apparatus may be configured for use with a molddefining a cavity and an opening extending into the cavity. Theexemplary vent apparatus may include a vent tube portion and a secondarytube portion. The vent tube portion may be configured to be locatedwithin the opening of the mold. Further, the vent tube portion mayextend from a first end region to a second end region along an axis andmay define a passageway extending from the first end region to thesecond end region configured to allow airflow between the cavity of themold and outside of the mold. The secondary tube portion may beconfigured to mate with the first end region of the vent tube portionand may include a valve region that extends perpendicular to the axiswhen the secondary tube portion is mated with the first end region ofthe vent tube portion. The valve region may define a plurality of slitstherethrough to allow airflow through the valve region from thepassageway of the vent tube portion to outside of the valve region.

One exemplary vent apparatus may include a vent tube portion extendingfrom a first end region to a second end region along an axis anddefining a passageway extending from the first end region to the secondend region. The exemplary vent apparatus may further include a secondarytube portion configured to mate with the first end region of the venttube portion. The secondary tube portion may include a valve region thatextends perpendicular to the axis when the secondary tube portion ismated with the first end region, and the valve region may define aplurality of slits therethrough to allow airflow through the valveregion from the passageway of the vent tube portion to outside of thevalve region.

In one or more embodiments, the valve region of the secondary tubeportion may be configured to restrict airflow in a first direction and asecond direction by the same amount of restriction, where the firstdirection is from outside of the valve region into the passageway of thevent tube portion and the second direction is from inside the passagewayof the vent tube portion to outside of the valve region.

One exemplary vent apparatus may include a vent tube portion extendingfrom a first end region to a second end region along an axis anddefining a passageway extending from the first end region to the secondend region. The exemplary vent apparatus may further include a secondarytube portion extending from a valve region to a insertion region anddefining a passageway extending from the valve region to the insertionregion. The insertion region may be configured to mate with the firstend region of the vent tube portion and the valve region may extendperpendicular to the axis when the insertion region is mated with thefirst end region. The valve region may be configured to restrict airflowin a first direction and a second direction by the same amount ofrestriction where the first direction is from outside of the valveregion into the passageway of the secondary tube portion and the seconddirection is from inside the passageway of the secondary tube portion tooutside of the valve region.

In one or more embodiments, the vent tube portion may define an outersurface, and the secondary tube portion may be configured to be matedaround the outer surface of the vent tube portion. Further, in one ormore embodiments, the secondary tube portion may be configured to bemated to the vent tube portion inside the passageway of the vent tubeportion.

In one or more embodiments, the valve region may define a surface facingaway from the vent tube portion and extending perpendicular to the axiswhen the secondary tube portion is mated with the first end region ofthe vent tube portion.

The above summary is not intended to describe each embodiment or everyimplementation of the present disclosure. A more complete understandingwill become apparent and appreciated by referring to the followingdetailed description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a simple rotational mold that may use a TEFLONtube for ventilation.

FIG. 2 is a cross-sectional view of an exemplary vent apparatus insertedinto the mold of FIG. 1.

FIG. 3 is a cross-sectional view of an exemplary vent apparatus.

FIG. 4 is a cross-sectional view of the vent apparatus of FIG. 3 showinga vent tube portion and secondary tube portion coupled together.

FIGS. 5-6 are diagrammatic overhead views of exemplary secondary tubeportions.

FIGS. 7-8 are side views of exemplary secondary tube portions.

FIGS. 9-10 are side views of exemplary secondary tube portions afteropening to allow airflow therethrough.

FIG. 11 is a cross-sectional view an exemplary vent apparatus insertedinto the mold of FIG. 1 with the secondary tube portion after beingopened to allow airflow therethrough.

FIGS. 12-15 are a cross sectional views of exemplary vent apparatuses.

FIGS. 16-18 include multiple views of exemplary vent apparatuses.

FIG. 19 is a perspective view of another exemplary vent apparatus.

FIG. 20 is a cross-sectional view of an exemplary vent tube portion ofthe vent apparatus of FIG. 19.

FIG. 21 is a cross-sectional view of an exemplary secondary tube portionof the vent apparatus of FIG. 19.

FIG. 22 is a cross-sectional view of the vent tube portion and thesecondary tube portion coupled (e.g., mated) together.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following detailed description of illustrative embodiments,reference is made to the accompanying figures of the drawings which forma part hereof, and in which are shown, by way of illustration, specificembodiments which may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from (e.g., still falling within) the scope of the disclosurepresented hereby.

Exemplary apparatus shall be described with reference to FIGS. 1-22. Itwill be apparent to one skilled in the art that elements from oneembodiment may be used in combination with elements of the otherembodiments (e.g., mating functionality described with respect to oneembodiment may be used in any of the other embodiments), and that thepossible embodiments of such apparatus using combinations of featuresset forth herein is not limited to the specific embodiments shown in thefigures and/or described herein. Further, it will be recognized that theembodiments described herein may include many elements that are notnecessarily shown to scale. Still further, it will be recognized thatthe size and shape of various elements herein may be modified but stillfall within the scope of the present disclosure, although certain one ormore shapes and/or sizes, or types of elements, may be advantageous overothers.

The present disclosure describes vent apparatus configured to be locatedin an opening in a mold. The vent apparatus may extend from outside ofthe mold to inside the mold and may be configured to selectively allowgas to move therebetween to, e.g., prevent pressure differentialsbetween the inside and outside of the mold thereby causing blowholes,deformed or scrap parts, and/or other abnormalities.

The exemplary embodiments will be described herein within reference to ageneral mold 10 as depicted in FIG. 1. In this example, the mold 10 maydefine a generally rectangular box-like shape. The mold 10 may include amold wall 12. The inner surface 14 of the mold wall 12 may define acavity 16 within which an article may be molded. The mold wall 12 mayfurther define a vent hole 18 extending therethrough. In other words,the vent hole 18 may connect the environment outside of the mold 10 tothe cavity 16.

As shown in FIG. 2, an exemplary vent apparatus 20 may be located in theopening 18 of the mold 10 (e.g., extending through the opening 18 of themold 10). The vent apparatus 20 may extend a distance 24 into the cavity16 measured from the inner surface 14 of the mold wall 12 to a valveregion 22 of the vent apparatus 20.

The vent apparatus 20 may include a vent tube portion 30 and a secondarytube portion 50 as shown in the cross-sectional view of FIG. 3. The venttube portion 30 may be configured to be reused with a mold 10 and thesecondary tube portion 50 may be configured for a selected number ofuses, such as, e.g., one use, two or more uses, three or more uses, etc.

The vent tube portion 30 may extend from a first end region 32 to asecond end region 34 and may define a passageway, or channel, 36extending from the first end region 32 to the second end region 34. Thepassageway 36 may be configured for the transmission of gases to andfrom the cavity 16 of the mold 10. The vent tube portion 30 may havevarious shapes and/sizes. For example, the vent tube portion 30 may beabout 4 inches to about 36 inches such as, e.g., about 5 inches, about 6inches, about 7 inches, about 8 inches, or any other number through 36inches. Further, for example, an inside diameter 38 of the vent tubeportion 30 may be about 0.5 inches to about 4 inches such as, e.g.,about 0.75 inches, about 1 inch, about 1.25 inches, about 1.5 inches,about 1.75 inches, about 2 inches, about 2.5 inches, about 3 inches,about 4 inches, etc.

The vent tube portion 30 may include one or more materials configured towithstand the heat of a molding oven and also configured to not adhere,or stick, to flowable material used within the cavity 16 of the mold 10to mold an article. For example, the vent tube portion 30 may be formedof PTFE (TEFLON).

As shown, and in one embodiment of a vent apparatus, the secondary tubeportion 50 of vent apparatus 20 may be inserted into the passageway 36of the vent tube portion 30 as indicated by arrows 51. The secondarytube portion 50 may include a valve, or tip, portion 52 (e.g., domedvalve region, curvilinear valve region, etc.) and a cylindrical portion54 and a passageway 55 extending therein. The cylindrical portion 54 maybe located inside the opening 36 of the vent tube portion 30 while thevalve region 52 may be located outside of the vent tube portion 30. Thesecondary tube portion 50 completely inserted, or coupled to, the venttube portion 30 is shown in FIG. 4. As shown, a shoulder portion 59 ofthe secondary tube portion 56 may contact, or be adjacent to, the firstend region 32 of the vent tube portion 30 when completely, or fully,inserted.

In this embodiment, the secondary tube portion 50 may remain coupled tovent tube portion 30 (e.g., inserted within the opening) by aninterference, or friction, fit between the cylindrical portion 54 of thesecondary tube portion 50 and an inner surface 42 of the vent tubeportion 30.

The secondary tube portion 50 may include one or more materialsconfigured to melt, or burn off, after a selected amount of time withina molding oven (e.g., after a selected amount of heat has been applied,after a selected amount of time at a selected temperature, etc.). Thesecondary tube portion 50 may include silicone, polyethylene,polypropylene, and/or any other material (e.g., such as a polymer) withsimilar thermal properties to that of which is being molded. In at leastone embodiment, the secondary tube portion 56 may include two differentmaterials configured to melt, or burn off, at different temperatureslevels. Such different materials may be located in different regions ofthe secondary tube portion 50. In at least one embodiment, the secondarytube portion 50 may be formed entirely of silicone, which may provide ahigh temperature resistant material to increase the cycle life.

One or more slits 58 may extend through the valve region 52 of thesecondary tube portion 50 as shown in FIGS. 5-8. The slits 58 may beconfigured to allow gases to flow therethrough. The shape (e.g., curved,domed, biased in one direction, etc.) of the valve region 52 may allowgas to flow into the cavity 16 of the mold 10 easier than flowing out ofthe cavity 16. The slits 58 are shown opened in FIGS. 9-10.

The mold 10 with a flowable material 11 such as, e.g., a polymer,coalesced to the inner surface 14 of the mold wall 12 is shown in FIG.11. Further, the secondary tube portion 50 is shown with the slits 58open and configured for gases to flow into and out of the cavity 16 ofthe mold 10.

The exemplary vent apparatus may control the airflow of gasses into andout of a mold. For example, the exemplary vent apparatus may beconfigured to allow gas to flow into and out of the cavity of a moldwith substantially the same, or equal amount of, restriction. Further,for example, a secondary tube portion may be configured to allowopenings such as, e.g., slits, etc., to open in either direction (intoor out of the mold cavity) depending on which area (inside the cavity oroutside the cavity) has higher pressure. In other words, the secondarytube portion may be configured to provide two-way valve functionalitythat is not biased in either direction and airflow may be restricted bythe secondary tube portion in either direction by the same amount ofrestriction or control.

FIG. 12 includes two cross-sectional views of exemplary vent apparatus100. The vent apparatus 100 may include a vent tube portion 120extending from a first end region 124 to a second end region 126 anddefining a passageway 125 extending from the first end region 124 to thesecond end region 126. The vent apparatus 100 may further include asecondary tube portion 150 that extends from an insertion region 157 toa valve region 158 and defines a passageway 159 extending from theinsertion region 157 to the valve region 158.

As shown, a secondary tube portion 150 may be coupled, or mated, to(e.g., slide into) the first end region 124 of the vent tube portion120. More specifically, the insertion region 157 of the secondary tubeportion 150 may be located inside at least a part of the passageway 125of the first end region 124 of the vent tube portion 120. The innersurface 127 of the vent tube portion 120 may contact an outer surface ofthe insertion region 157 of the secondary tube portion 150. To restrictmovement of the secondary tube portion 150 with respect to the vent tubeportion 120 (e.g., to keep the secondary tube portion 150 from slidingdown the passageway 125 of the vent tube portion 120), the vent tubeportion 120 may define a larger inner diameter extending from the firstend region 125 and smaller inner diameter forming a step structure 122upon which at least part (e.g., the end or edge) of the insertion region157 of the secondary tube portion 150 may contact or nest. For example,the secondary tube portion 150 and the vent tube portion 120 may besized such that the secondary tube portion 150 may nest, or mate withthe vent tube portion 120. The step structure 122 created inside thevent tube portion 122 as well as a lip 152 of the valve region 128 ofthe secondary tube portion 150 (e.g., which may seat on the end or rim128 of the vent tube portion 120) may restrict, or restrain, movement ofthe secondary tube portion 150 (e.g., such that the secondary tubeportion 150 does not move after being nested within the vent tubeportion 120).

As described herein, the exemplary vent apparatus may be configured toallow gas to flow into and out of the cavity of a mold withsubstantially the same, or equal amount of, restriction. In at leastthis embodiment, the valve region 158 of the secondary tube portion 150may provide the airflow functionality described herein. For example, thevalve region 158 may define one or more, or a plurality ofopenings/apertures (e.g. slits) to, e.g., provide airflow through thevent tube (e.g., from inside the mold to outside of the mold, and viceversa). The number of slits may vary, although one or moreconfigurations or numbers of slits may be advantageous over others. Forexample, two cross slits from edge to edge may be used (e.g., forming an“X” as shown in FIG. 5, three slits extending across the flat end capmay be used (e.g., equally spaced as shown in FIGS. 16-18), four or moreslits may be provided from edge to edge, slits may extend only partiallyacross the flat end cap (e.g., at the center thereof, off centered,etc.), other patterns of slits may be defined therein, etc.

In the embodiment depicted in FIG. 12, the valve region 158 of thesecondary mold portion 150 may be perpendicular to an axis 156 alongwhich the vent apparatus 100 extends. The valve region 158 may furtherdefine a surface 154 (e.g., flat end cap) that is also flat, or planar,(e.g., flat end cap) that is normal to the axis 156 of the ventapparatus 100. It may be described as a flat cap at the top of thesecondary tube portion 150. The flat, or planar, nature of the valveregion 158 and/or surface 154 of the secondary tube portion 150 mayprovide two-way valve functionality that is not biased in eitherdirection. For example, airflow may be restricted in either direction bythe same amount of restriction. In other words, since the exemplaryembodiments in FIGS. 12-18 each have a planar valve region 158 andsurface 154 (e.g., flat end cap) defining openings or slits, eachembodiment in FIGS. 12-18 may allow airflow in either direction in andout of the mold with the same impedance.

Further, since the inside diameter of the passageway 125 of vent tubeportion 120 does not change within the addition of the secondary tubeportion 150, airflow through the vent tube portion 120 is notrestricted. In other words, the secondary tube portion 150 may notincrease the inside diameter of the passageway 125 of the vent tube 120such that the airflow normally provided by a vent tube portion 120having the same diameter is maintained.

FIGS. 13-15 depict additional exemplary vent apparatus 101 where asecondary tube portion 151 may be located around the outside of the venttube portion 121. As shown, the secondary tube portion 151 may notincrease the outside diameter of the vent tube portion 121 such that thevent tube portion 121 may still be inserted in a vent opening of a mold.The valve region 161 of the secondary tube portion 151 may take anynumber of forms described herein (e.g., flat end cap with slits,membranes configured to melt, or burn off, openings, etc.). As shown inFIG. 13, the vent tube portion 121 may define an outer surface 123 uponwhich the secondary tube portion 151 may be mated or coupled to (e.g.,around the outer surface 123).

FIGS. 16-18 depict additional exemplary vent apparatus 170 where asecondary tube portion 174 is located inside the opening of the venttube portion 172. Such embodiments showing the mating of the secondarytube portion with the vent tube portion may be similar to othersdescribed herein and will not be described in further detail. In the oneor more embodiments, the secondary tube portions may mate, or fit withinor around, the vent tube portion with an interference fit, or mayinclude any further wall structures or deformations in the walls thatmay provide additional holding forces when the two portions are mated.

As described herein, during the rotational molding process, encapsulatedgas, or air, within the mold may be heated during the “cooking” or“heating” process causing the gas, or air, to expand. During this gasexpansion process, pressure may build within the mold cavity and thepressure may be relieved. The relief process may be accomplished using avent tube that is located thru the wall of the mold allowing gasseswithin the mold to travel thru the tube and escape, and vice versa.

The flowable material that is placed, or located, into the mold (e.g.,in the cavity of the mold) before the molding process begins maynormally be in a powder form. If the vent tube was not covered or sealed(e.g., allowed to be a hollow tube) during the whole rotational moldingprocess, flowable material may escape through the vent tube and spillout of the mold. Therefore, the end of the vent tube located inside themold cavity may be covered (e.g., sealed as described herein) while themolding process begins to prevent flowable material spillage through thevent tube.

As the mold heats up, the flowable material within the mold begins tomelt, become somewhat of a “plasma”-type of material, and begin layeringitself on the interior walls of the mold. At this point, the flowablematerial is no longer in powder form and the opportunity for spillagethrough the vent tube may have diminished. At the same time, a membrane(e.g., such as one or more membrane regions described herein) placed, orlocated, on the end or towards the end of the vent tube may also meltdue to the heat and may allow the encapsulated gasses, or air, inside ofthe mold cavity to escape. Additionally, as described herein, exemplaryvent apparatus may be configured to allow airflow into and out of a moldcavity (e.g., after the membrane regions melt). Further, the exemplaryvent apparatus may also be configured to act as a stop valve forflowable material (e.g., resin) before the flowable material coalescesto walls of a mold cavity (e.g., before the membrane regions melt).

Another exemplary vent apparatus 200 (e.g., which uses regions presentduring parts of the molding process but which melt away and are nolonger present during other parts of the molding process) for use in amold is depicted in FIG. 19. The vent apparatus 200 may include a venttube portion 220 and a secondary tube portion 250. The secondary tubeportion 250 may be configured to mate with the vent tube portion 220 toseal (e.g., selectively seal) a passageway of the vent tube portion 220.

The vent tube portion 220 may be configured to be located inside theopening a mold extending into the cavity of the mold. The vent tubeportion 220 may extend from a first end portion 222 to a second endportion 224 along an axis 225. The vent tube portion 220 may define apassageway 226 extending from the first end portion 222 to the secondend portion 224. Additionally, the vent tube portion 220 defines anouter surface 228 and an inner surface 229. As shown, the vent tubeportion 220 is generally cylindrically shaped along the axis 225.

As shown in FIG. 20, the vent tube portion 220 may define a vent tubeouter diameter 230 that may be various sizes due to physical size of theitems being molded. Larger diameter vent tube portions 220 may berequired on larger volume molds to allow a larger quantity ofencapsulated air to escape. If too small of a vent tube portion 220 isused, air may not escape fast enough leaving the mold pressurized, whichmay cause air to escape out of the mold in areas not intended, leavingsmall holes in the plastic item being molded. The vent tube diameter 230may be about 0.5 inches to about 4 inches such as, e.g., about 0.75inches, about 1 inch, about 1.25 inches, about 1.5 inches, about 1.75inches, about 2 inches, about 2.5 inches, about 3 inches, about 4inches, etc.

The first end portion 222 of the vent tube portion 220 may define amating region 240 configured to mate with the secondary tube portion250. The mating region 240 may have a mating region outer diameter 242that is less than the vent tube outer diameter 230. Additionally, themating region 240 may define a mating region length 246 extendingparallel to the axis 225 (e.g., a length that is less than a distance ofthe secondary tube portion 250 from the most proximal membrane regiondefined by the secondary tube portion 250 to the proximal end thereof).

The first end portion 222 may further define an annular protrusion 244extending radially from the outer surface 228. The annular protrusion244 may be configured to engage the secondary tube portion 250 when thesecondary tube portion 250 is mated to the first end portion 222. Anyother engaging structure may be added to the first end portion 222 or tothe secondary tube portion 250 (e.g., the inner surface thereof) toassist in retaining the secondary tube portion 250 on the first endportion 222 (e.g., burrs, indents, radial structures, etc.).

The secondary tube portion 250 may be configured to mate with the firstend portion 222 (e.g., mating region 240 of the first end portion 222)of the vent tube portion 220 to seal the passageway 226 proximate, orat, the first end portion 222. One or more membrane regions 260 of thesecondary tube portion 250 may be configured to melt, or burn off,during a mold process to unseal, or open, the passageway 226 therebyallowing airflow through the passageway 226 either out of the moldcavity or into the mold cavity. As shown, the secondary tube portion 250may include more than one membrane regions 260 (e.g., a plurality ofmembrane regions 260).

The secondary tube portion 250 may include or be formed of one or morematerials such as, e.g., polypropylene, polyethylene, and/or any othermaterial (e.g., such as a polymer) with similar thermal properties tothat of which is being molded, etc. In at least one embodiment, thesecondary tube portion 250 may be formed, or manufactured, usinginjection molding.

The membrane regions 260 may define a thickness that is less than thewall thickness of the remainder of the secondary tube portion 250. Thethickness of the membrane regions 260 may depend on the article beingformed in the mold. For example, thicker molded articles may requiremore flowable material, more heat, and/or more time to process. As such,the membrane regions 250 may need to be different thickness such thatthey melt, or burn off, at the appropriate time for the appropriatemolded article.

In other words, due to physical size of parts and the amount of flowablematerial, or plastic powder, that may be required to “melt” within themold, various thicknesses of membrane regions 260 may be required. Thismay be due to the amount of heat and time that may be required to meltlarger quantities of flowable material. For example, if the membraneregions 260 are too thin, the membrane regions 260 may melt before theflowable material is melted causing flowable material to leak thru thevent tube portion 220. If the membrane regions 260 are too thick, themembrane regions 260 may not melt at all causing the entrapped air toescape out of the mold in areas not intended leaving small holes in thearticle being molded.

For example, the membrane regions 260 may have a thickness of about0.001 inches to about 0.010 inches such as, e.g., about 0.001 inches,about 0.002 inches, about 0.003 inches, about 0.004 inches, about 0.005inches, about 0.006 inches, about 0.007 inches, about 0.008 inches,about 0.009 inches, about 0.010 inches, etc. Additionally, each of themembrane regions 260 may not have the same thickness. In other words,some membrane regions 260 may have different thicknesses than others.

As shown in FIG. 21, the secondary tube portion 250 may be described asincluding a cylindrical body 252 extending from a proximal end portion254 to a distal end portion 256 and defining a channel 258 from theproximal end 254 portion to the distal end portion 256. An end surfaceportion 259 of the secondary tube portion 250 may cover the channel 258at the distal end portion 252. As shown, the end surface portion 259 mayinclude a membrane region 260.

The orientation of the membrane regions 260 may be described in terms ofthe axis 225. For example, membrane regions 260 may extend perpendicularor parallel to the axis 225. As shown, the membrane region 260 of theend surface portion 259 (e.g., an end membrane) is perpendicular to theaxis 225. Further, the cylindrical body 252 may define one or moremembrane regions 260 (e.g., one or more body membranes). As shown, themembrane regions 260 defined by the body 252 are parallel to the axis225. In one or more embodiments, the end surface portion 259 includesonly a membrane region at the center thereof (e.g., such a membraneregion being suspended from portions of the body, such a membrane beinga flat membrane with no other features or structure providing supporttherefore, such a membrane region covering an area greater than 50percent of an inner cross-section area of the secondary tube portion 250taken perpendicular to the axis 225, such a membrane region covering anarea greater than 60 percent of an inner cross-section area of thesecondary tube portion 250 taken perpendicular to the axis 225, such amembrane region covering an area greater than 80 percent of an innercross-section area of the secondary tube portion 250 taken perpendicularto the axis 225, etc.).

Including one or more membrane regions (e.g., primary and/or auxiliary)at different orientations relative to one another (e.g., orthogonal orat any other angle relative to each other) and/or at different locations(e.g., cylindrical body locations versus end locations) may provideadditional benefits. For example, there may be times when a membraneregion (e.g., the end membrane) may not melt completely or effectively.With use of additional or multiple membrane regions at differentorientations relative to one another and/or at different locations, theeffects from one membrane region not completely melting are reduced.

The secondary tube portion 250 is shown mated with the vent tube portion220 in FIG. 22. As shown, the secondary tube portion 250 may extend overat least a portion of the outer surface 228 of the vent tube portion220. For example, the secondary tube portion 250 may extend over aportion of the first end portion 222, or more specifically, the matingregion 240.

The mating region 240 and the secondary tube portion 250 may be sizedwith respect to each to provide coupling therebetween. For example, thesecondary tube portion 250 may define a secondary tube portion length267 that is longer than the mating region length 246. Further, forexample, the secondary tube portion 250 may define a secondary tubeportion inner diameter 265 that is greater than or equal to the matingregion outer diameter 242.

The mating between the secondary tube portion and the vent tube portionmay be accomplished with any other mating configurations describedherein. For example, the secondary tube portion may extend within atleast a portion of the inner surface 229 of the vent tube portion 220(e.g., extend within and along at least a portion of the inner surfaceof the vent tube portion such as shown in the embodiment of FIG. 12 orFIG. 16).

The membrane regions 260 may be sized in terms of the area of passageway226 of the vent tube portion 250 and/or of the channel 258 of thesecondary tube portion 250. For example, each of the passageways 226 ofthe vent tube portion 250 and the channel 258 of the secondary tubeportion 250 may be described as defining an inner cross-section areataken perpendicular to the axis 225. Further, each of the one or moremembrane regions 260 may be described as defining an area along whichthe membrane region 260 lies (e.g. a planar area in the case of themembrane region defined by the end surface portion 259, an area of anarc in the case of the membrane regions defined in the cylindrical bodyparallel to axis 225, etc.). A combined area of all of the areas of theone or more membrane regions 260 may be greater than the innercross-section area of either of the passageway 226 or the channel 258taken orthogonal to the axis 225.

The complete disclosure of the patents, patent documents, andpublications cited in the background, the detailed description ofexemplary embodiments, and elsewhere herein are incorporated byreference in their entirety as if each were individually incorporated.

Illustrative embodiments of this invention are discussed and referencehas been made to possible variations within the scope of this invention.These and other variations, combinations, and modifications in theinvention will be apparent to those skilled in the art without departingfrom the scope of the invention, and it should be understood that thisinvention is not limited to the illustrative embodiments set forthherein.

What is claimed is:
 1. A vent apparatus for use in a mold defining an opening comprising: a vent tube portion configured to extend through the opening of the mold, wherein the vent tube portion extends from a first end portion to a second end portion along an axis and defines a passageway extending from the first end portion to the second end portion, wherein the vent tube portion defines an inner surface and an outer surface; and a secondary tube portion configured to mate with the first end portion of the vent tube portion to seal the passageway at the first end portion, wherein the secondary tube portion comprises an inner surface and an outer surface along an axis and extends over at least a portion of the outer surface of the vent tube portion or extends within and along at least a portion of the inner surface of the vent tube portion, wherein the secondary tube portion defines one or more membrane regions configured to melt during a mold process to unseal the passageway.
 2. The vent apparatus of claim 1, wherein the vent tube portion defines a vent tube outer diameter, wherein the first end portion of the vent tube portion defines a mating region having a mating region outer diameter that is less than the vent tube outer diameter.
 3. The vent apparatus of claim 1, wherein the first end portion of the vent tube portion defines a mating region, wherein the mating region defines a mating region length extending along the axis, wherein the secondary tube portion defines a secondary tube portion length that is longer than the mating region length.
 4. The vent apparatus of claim 1, wherein the vent tube portion defines a vent tube outer diameter, wherein the secondary tube portion defines a secondary tube portion inner diameter that is less than the vent tube outer diameter.
 5. The vent apparatus of claim 1, wherein the first end portion of the vent tube portion defines an annular protrusion extending radially from the outer surface of the vent tube portion configured to engage the secondary tube portion when the secondary tube portion is mated to the first end portion.
 6. The vent apparatus of claim 1, wherein the one or more membrane regions of the secondary tube portion comprise a plurality of membrane regions.
 7. The vent apparatus of claim 1, wherein the one or more membrane regions of the secondary tube portion comprise a membrane region extending perpendicular to the axis when the secondary tube portion is mated to the first end portion.
 8. The vent apparatus of claim 1, wherein the one or more membrane regions of the secondary tube portion comprise at least one membrane region extending parallel to the axis when the secondary tube portion is mated to the first end portion.
 9. The vent apparatus of claim 1, wherein the secondary tube portion comprises a cylindrical body extending from a proximal end portion to a distal end portion and defining a channel from the proximal end portion to the distal end portion, wherein the secondary tube portion further comprises an end surface portion covering the channel at the distal end portion, wherein the end surface portion defines a membrane region of the one or more membrane regions.
 10. The vent apparatus of claim 9, wherein the end surface portion comprises only a membrane region at the center thereof.
 11. The vent apparatus of claim 9, wherein the cylindrical body defines at least one membrane region of the one or more membrane regions.
 12. The vent apparatus of claim 1, wherein the passageway of the vent tube portion defines an inner cross-section area taken perpendicular to the axis, wherein each of the one or more membrane regions of the secondary tube portion define an area, wherein a combined area of all of the areas of the one or more membrane regions is greater than the inner cross-section area of the channel. 